The classic Baconator and Hot 'N Juicy sandwiches are now joined by burgers piled high with extravagant ingredients such as lobster and caviar. They’re priced at just above $16, according to the Burger Business blog.

Here’s the catch: They’re available for only a limited time. And only in Japan.

Since returning to the Japanese market late last year after exiting in 2009, Wendy’s has rolled out a series of indulgent menu offerings. It debuted with a $16 burger lavished with foie gras and truffle sauce, followed by a $12.50 burger featuring chili and Iberian bacon.

Wendy’s American fare is much more subdued -- mostly in the $5 to $6 range. But the chain, along with competitors such as McDonald’s and KFC owner Yum Brands, is betting heavily on foreign expansion.

And it's also taking cues from the onslaught of so-called better burger fast-casual brands in the U.S. Chains such as Five Guys Burger & Fries and Smashburger are among the fastest-expanding quick-service restaurant companies in the country, luring customers with menus that offer value, high-quality ingredients and a premium experience that often includes customization options.

McDonald’s share makes up half of the quick-service burger segment -- which is the largest sector by revenue in the entire restaurant industry. But fast-casual chains grew sales by 20.8% last year, while the overall category expanded just 3.7%, according to a report last week from research group Technomic.

Smashburger’s sales grew more than 71% last year, while Five Guys watched its sales boom 24%, according to Technomic.

Burger chains are the biggest business in the restaurant industry, pulling in $69 billion in sales each year. Nearly nine in 10 consumers say they grab burgers away from home at least once a month. Half of that business goes to McDonald's -- the behemoth that in recent years has upgraded its sandwich...

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